1. Field of the Invention
The present invention relates to a new and improved method of, and apparatus for, conveying solid particles, typically abrasive or grinding particles and the like, to an apparatus, particularly a remotely situated apparatus for loading or charging free-flowing or fluent cutting jets with such solid particles, for instance, fluid jet-abrasive cutting apparatuses. Solid particles, preferably in a predetermined quantity, are removed from a container or hopper, introduced into a transport or carrier medium and in conjunction therewith are delivered to the cutting apparatus and held in readiness for charging the cutting jet with these solid particles.
2. Discussion of the Background and Material Information
Liquid jet-cutting apparatuses, using as the cutting implement a thin, free-flowing or fluent cutting jet possessing high kinetic energy, have been beneficially employed for cutting sheet- or surface-like materials. Abrasive cutting is usually required for this type of processing or machining of workpieces or materials possessing high strength, in which case the high velocity fluid cutting jet is charged or laden with solid particles, that is to say, cutting or abrasive particles or the like. When working with abrasive cutting equipment the cutting jet effluxing from a nozzle finally flows through a focusing or constricting nozzle. A negative or lower pressure is produced in a mixing chamber of the cutting jet equipment, by means of which solid particles are sucked out of a container or hopper which is preferably equipped with a dosing device.
Containers or hoppers or the like, which hold in readiness the solid particles, are connected by transport or conveying means, such as for instance, a hose or a line with the cutting apparatus or cutting head, and the conveyance of the solid particles is undertaken by the negative or reduced pressure formed in the cutting head. What is disadvantageous in this regard is that for an adequate transport of the solid particles the transport line or conduit must be of short length, and thus, the distance between the container or hopper and the cutting head is essentially limited to a maximum of 5 meters. Furthermore, especially when interrupting the flow of the solid particles, they tend to settle in the carrier medium because of their greater specific weight, and hence, can obstruct or clog the transport or connection line or the like. Also, small containers or intermediate receptacles are frequently arranged above the cutting head in order to improve the delivery of the solid particles. Here, upon interrupting the flow of the cutting jet there can arise an undesired further feeding of the solid particles into the mixing chamber because of the weight of such solid particles. Furthermore, there is required a controlled filling of the intermediate receptacle, as a function of particle consumption, from a remotely situated supply container or hopper. When the solid particles are pneumatically transported, there is required an interrupted re-filling operation with intermediate pumping empty of the transport or conveying lines.
In European Patent Application No. 0,152,223, published Aug. 21, 1985, there is disclosed a method and apparatus for producing cutting jets laden with abrasive particles. Transport of the abrasive or solid particles through a distance of 100 meters or more is contemplated. A carrier medium, particularly air, is delivered to a venturi, where there are admixed abrasive particles furnished from a supply container, the mixture is transported and the abrasive particles are removed in a separator and delivered by a pipe having a small diameter to a venturi containing a high-pressure cutting jet. What is here disadvantageous is that at the start of the operation there is required a great deal of time during which the abrasive or solid particles are delivered from the supply container to the separator. Furthermore, shutting-off of the cutting jet only can be feasibly undertaken when the pipe- and infeed line are extensively freed of abrasive particles, because otherwise there exists the danger of obstructing or clogging this line.